Stabilized tetraethyllead compositions



Patented July 20, 1954 STABILIZED TETRAETHYLLEAD COMPOSITIONS Eugene F. Hill, Detroit, and David 0. De Pree,

Birmingham, Mich., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application January 22, 1952, Serial No. 267,686

This invention relates to the stabilization of hydrocarbon fuels containing organo lead antiknock compounds. Our invention also relates to the inhibition of attack by oxygen of the antiknock material itself.

Hydrocarbon fuels under present requirements of high-compression engines are almost universally treated with antiknock compounds, the principal ingredient of which is tetraethyllead.

Both automotive and aircraft fuels are commonly blended with tetraethyllead before use. Such blending imposes a point of instability in the finished fuel, since the tetraethyllead is susceptible to some deterioration by contact with oxygen during the blending, storage and handling operations, with consequent formation of haze, loss of some antiknock value, and lessened performance in the engine. This point of attack is often overlooked in certain automotive fuels, as the base stock is often unstable itself. If, however, a stabilizing ingredient were added which is capable of protecting only the fuel, the attack upon the tetraethyllead would then become apparent. In aircraft fuels the reverse is true, that is the protection must center upon the antiknock additive, as the fuel itself is relatively stable. Furthermore, this phase of the problem becomes relatively more important in aircraft fuels, since the tetraethyllead content of such fuels is generally several times that present in automotive fuels.

Heretofore, it has not been possible to protect such fuels for internal combustion engines effectively by means of a single substance against the two above described separate but related deleterious effects of contact with oxygen during the refining, manufacturing, blending, storage and handling operations. Furthermore, because of the specifications imposed on fuels by the rigid requirements of present day engines, particularly aircraft engines, it is essential that any material capable of protecting such fuels against deterioration must be effective in extremely small quantitles, on the order of one pound of additive per five thousand gallons of fuel, so that secondary problems do not arise through their use.

It is therefore an object of our invention to provide means for protecting such antiknock compounds against deterioration in the presence of oxygen. Another object of our invention is to provide means for stabilizing lead-containing hydrocarbon fuels for internal combustion spark engines during the manufacturing, handling and storage of such fuelsprior to their use. It is also an object of our invention to provide fuels con- 8 Claims. Cl. 4469) taining tetraethyllead in which there is essentially no loss in performance characteristics due to such deterioration of the tetraethyllead during blending, storage and handling. Still further objects of our invention will appear from the description of our invention as hereinafter disclosed.

The above objects can be accomplished by practicing our invention which comprises adding to tetraethyllead or materials containing tetraethyllead a small proportion of a substance derived from the class of alkylaminomethylhydroquinones. In general, the stabilizer of our invention are those compounds prepared by reaction between formaldehyde, amines and hydroquinones.

The compounds of our invention can be further defined in terms of the general formula wherein y is 1 or 2, R1, R2 and R3 are the same or different, and represent hydrogen or alkyl radicals. We have further found that, while one of R1 and R2 can be hydrogen, at least one of these groups must be alkyl to obtain effective stabilizing compounds. By the term alkyl we mean to include straight and branched chain saturated hydrocarbon radicals and saturated cyclic hydrocarbon radicals. The latter can also be referred to as cycloalkyl radicals. We have found that in those compounds of our invention wherein R3 is hydrogen, we obtain the most effective antioxidants when y is 2. However, when R3 is alkyl, we obta'm the most potency when 1/ is 1. We prefer that the two hydroxy groups be para to each other, although some effectiveness is obtained with the meta and ortho compounds.

Typical examples of specific embodiments of the antioxidants of our invention include 2 ,5-bis- (dimethylaminomethyl) hydroquinone, 2-methyla(dimethylaminomethyl) hydroquinone, 2,5-bis- (diethylaminomethyl) hydroquinone, 2,5-bis(din-propylaminomethyl) hydroquinone, 2,5-bis(din butylaminomethyl) hydroquinone, 2,5 bis (methylaminomethyl) hydroquinone, 2,5-bis(N- ethyl-N-n-butylaminomethyl) hydroquinone, and 2f=,5-bis (cyclohexylaminomethyl) hydroquinone.

In the foregoing examples we have indicated uncertainty in the position occupied on the benzene nucleus by the alkylaminomethyl group by the prefix a. For purposes of further clarification, therefore, the compounds of our invention may be defined as the reaction products obtained by reacting hydroquinones, as for example hydroquinone and toluhydroquinone, with formaldehyde and amines, such as dimethylamine, diethylamine, dipropylamine, diamylamine, methylamine, ethylamine, propylamine, cyclohexylamine, methylethylamine, propylethylamine, and ethyl-n-butylamine.

The absorption of oxygen can be measured directly by the standard method of the American Society of Testing Materials for determination of the Oxidation Stability of Gasoline (1nduction Period Method), ASTM designation: D525-46, as fully described in part III-A, ASTM Standards for 1946. According to this method the induction period is the period during which there is no absorption of oxygen by the test material as indicated by a drop in pressure, when placed in a testing bomb maintained at a temperature of 100 C. with an initial pressure of 100 pounds per square inch gauge of oxygen. The Induction Period Increase (IPI) is the in crease in the duration of this period caused by the addition of a protective substance, and is a direct measure of the protection afforded by such additive. Thus, the longer the IPI the more effective is the stabilizer. On the contrary, certain substances exert a pro-oxidant effect in which a negative IPI is obtained, that is, the duration of the induction period, or period of no absorption of oxygen, is less than in the absence of the additive.

To illustrate the protection afforded to hydrocarbon solutions of tetraethyllead by the compounds of our invention we conducted a series of tests in which hot-acid isooctane containing 4.6 milliliters of tetraethyllead per gallon was heated at a temperature of 100 C. in a stainless steel bomb with oxygen added to an initial pressure of 100 pounds per square inch gauge. Under these conditions the pressure in a bomb containing only isooctane and a tetraethyllead antiknock mixture underwent a sharp drop after four hours, indicating absorption of oxygen by the fuel mixture. The minimum con centration of each of several additives required to prevent a drop in pressure in a bomb during a period of 16 hours at a temperature of 100 C. was thereupon determined. Thus, the effective concentration shown in Table III is the minimum quantity of additive required, expressed as milligrams per 100 milliliters of fuel, to afford a greater than four-fold increase in the stability of the fuel.

By reference to Table I, it is apparent that typical compounds (Nos. 1 and 2) afford a fourfold increase in the stability of the fuel at an extremely low concentration level. Nos. 1 and 2 can be compared with No. 3, a material widely employed as a commercial hydrocarbon antioxidant, whereupon it is shown that the compounds of our invention are efiective at concentrations of one-third to two-thirds the required concentration of this material.

Similar results are obtained when other compounds of our invention are employed to stabilize hydrocarbon fuels containing tetraethyllead. For example when we employ 2,5-bis(di-n-butylaminomethyl)hydroquinone, 2,5 bis di npropylaminomethyl) hydroquinone, 2,5-bis(N- ethyl N n butylaminomethyl)hydroquinone, 2,5-bis(diethylaminomethyl)hydroquinone, 2,5- bis(methylaminomethyl) hydroquinone and 2,5- bis (cyclohexylaminomethyl) hydroquinone at concentrations in the range of between about 0.1 and 1 milligram per 100 ml. of fuel, effective protection is obtained.

We do not intend, however, that our invention be restricted to such concentrations as in the specific examples cited above. Thus the quantity of tetraethyllead stabilizer required is dependent both upon the concentration of the tetraethyllead and the degree of instability of the fuel carrier. Thus we can employ between about 0.1 and 15 milligrams per 100 ml. of tetraethyllead-hydrocarbon solution.

When our materials are employed directly in tetraethyllead or in tetraethyllead antiknock compounds comprising, for example, chlorine and bromine scavengers, we can employ somewhat larger quantities of our stabilizer. For example in such compositions we prefer to employ between about 0.1 and 20 parts of alkylaminomethyl hydroquinone per parts or contained tetraethyllead. Thus our compounds can be satisfactorily employed in a wide range of concentrations and we do not intend that our invention be restricted to the specific quantities mentioned herein.

We have disclosed a number of preferred embodiments of our invention and illustrated several means whereby protection can be afforded to tetraethyllead and organic materials sensitive to attack by oxygen containing tetraethyllead. Our invention is not intended to be limited to the specific embodiments of our invention herein or to the means described herein for obtaining the advantages possible in employing our compounds, as other methods of practicing our invention will be apparent to those skilled in the art.

We claim:

1. A new composition stable to oxidation consisting essentially of tetraethyllead and, in quantity sufficient to inhibit deterioration in the presence of oxygen, a di-substituted dihydroxybenzene, one substituent of which is an alkylaminomethyl containing 1 to 6 carbon atoms and the second substituent of which is selected from the group consisting of methyl and alkylaminomethyl containing 1 to 6 carbon atoms.

2. A new composition stable to oxidation consisting essentially of a petroleum hydrocarbon fuel, stable to oxidation, and a tetraethyllead antiknock additive, the presence of said antiknock additive resulting in a fuel composition normally tending to deteriorate in the presence of oxygen, and, in quantity sufficient to inhibit said deterioration, a (ii-substituted dihydroxybenzene, one substituent of which is an alliylaminomethyl containing 1 to 6 carbon atoms and the second substituent of which is selected from the group consisting of methyl and alkylaminomethyl containing 1 to 6 carbon atoms.

3. The composition of claim 1 wherein the disubstituted dihydroxybenzene is 2,5-bis(dimethylaminomethyl) -hydroquinone.

4. The composition of claim 1 wherein the disubstituted dihydroxybenzene is 2,5-bis(di-n-butylaminomethyl) -hydroquinone.

5. The composition of claim 1 wherein the disubstituted dihydroxybenzene is 2,5-bis(diethylaminomethyl) -hydroquinone.

6. The composition of claim 1 wherein the disu'bstituted dihydroxybenzene is 2,5-bis(cyclohexylaminomethyl) -hydroquinone.

7. The composition of claim 1 wherein the disubstituted dihydroxybenzene is the reaction product of toluhydroquinone, formaldehyde and dimethylamine.

8. A new composition stable to oxidation consisting essentially of between about 0.1 and 20 parts of a (ii-substituted dihydroxybenzene, one substituent of which is an alkylaminomethyl containing 1 to 6 carbon atoms and the second substituent of which is selected from the group consisting of methyl and alkylaminomethyl containing 1 to 6 carbon atoms, and 100 parts of tetraethyllead.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,361,337 Walters Oct. 24, 1944 2,553,441 Chenicek May 15, 1951 

1. A NEW COMPOSITION STABLE TO OXIDATION CONSISTING ESSENTIALLY OF TETRAETHYLLEAD AND, IN QUANTITY SUFFICIENT TO INHIBIT DETERIORATION IN THE PRESENCE OF OXYGEN, A DI-SUBSTITUTED DIHYDROXYBENZENE, ONE SUBSTITUENT OF WHICH IS AN ALKYLAMINOMETHYL CONTAINING 1 TO 6 CARBON ATOMS AND THE SECOND SUBSTITUENT OF WHICH IS SELECTED FROM THE GROUP CONSISTING OF METHYL AND ALKYLAMINOMETHYL CONTAINING 1 TO 6 CARBON ATOMS. 